On all of our "C" rides someone knowledgeable brings up the rear. But one problem we do have a lot of is new people coming up to one of us at the end complaining "This is advertised as a 14 mph ride and we spent a lot of time at 16" (or 16 and 18, etc.). We have to politely explain that 14 means an average of 14 and the ride will often exceed that, but at the end we will have averaged 14.